On Wed, 6 Sep 2023 18:34:29 GMT, Mandy Chung <[email protected]> wrote:
> This reimplements
> `sun.reflect.ReflectionFactory::newConstructorForSerialization` with method
> handles.
>
> This API currently generates the bytecode which fails the verification
> because `new C; invokespecial A()` where the given class `C` and invoke a
> no-arg constructor of `C`'s first non-`Serializable` superclass `A` is not a
> valid operation per the VM specification. VM special cases the classes
> generated for reflection to skip verification for the constructors generated
> for serialization and externalization. This change will allow such VM hack
> to be removed.
>
> A `jdk.reflect.useOldSerializableConstructor` system property can be set to
> use the old implementation in case if customers run into any compatibility
> issue. I expect this change has very low compatibility risk. This system
> property is undocumented and will be removed in a future release.
src/java.base/share/classes/jdk/internal/reflect/MethodHandleAccessorFactory.java
line 127:
> 125: static ConstructorAccessorImpl
> newSerializableConstructorAccessor(Class<?> decl, Constructor<?> ctor) {
> 126: if (!constructorInSuperclass(decl, ctor)) {
> 127: throw new UnsupportedOperationException(ctor + " not a
> superclass of " + decl.getName());
Notice in JShell 20, you could do this:
jshell> import sun.reflect.ReflectionFactory;
jshell> var rf = ReflectionFactory.getReflectionFactory()
jshell> var c = rf.newConstructorForSerialization(String.class,
Boolean.class.getConstructor(boolean.class))
jshell> String d = (String) c.newInstance(false)
jshell> d.length()
which ends up in an NPE for `d.value` is null. This UOE is technically a new
behavior that should be mentioned in the CSR.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/15600#discussion_r1317878647
